The study of fish neuroendocrinology has had a significant impact on our general understanding of the functional roles and evolution of a variety of neurochemical messengers and systems. Not only do fish possess unique neuroendocrine features, they have also been and remain an important vertebrate models for the discovery of new neuropeptides. In the last fifty years, neuroendocrinologists have documented a complex and seemingly infinite number of interactions between hormones and nerve st...